Fast ions in a laser plasma

Heating of spherical targets by intense laser radiation in the ''Kalmar'' istallation not only resulted in the spherically-symmetric ejection of thermal ions of the plasma but also, as various methods revealed, the jet-like emission of fast ions with energies approximately 0.5 MeV. An analysis of the possible acceleration mechanisms showed that the effect is due to ponderomotive acceleration of the ions in the critical density region by the resonantly amplified electric field of the laser radiation. A theory of resonance acceleration of ions is developed in which nonlinear interaction between plasma waves in the critical density region is taken into account. Estimates of the energy and number of fast ions are in agreement with the experimental data